where sigma is the constant of the Stefan-Boltzmann Law of blackbody radiation.

The pyrgeometer equipped with a thermocouple reads a voltage U_emf from which R_eff is computed as U_emf/S, where S is a sensitivity factor determined by calibration to a reference. The voltage is proportional to the difference between the temperature of the surface and that of the atmosphere as measured by the pyrgeometer detector.

Anders Ångström thus reported in 1915 measurements of a quantity named DLR or "back radiation" according to the formula

DLR = U_emf/S + sigma T^4 (*)

defining DLR by an instrument reading of U_emf/S and Stefan-Boltzmann's Law for blackbody radiation into a surrounding at 0 K. The formula (*) defining back radiation = DLR through an instrument, is presented as a basic pillar of the greenhouse effect GHE with the trace CO2 given the capability to change DLR with a warming effect on the Earth surface.

Anders Ångström constructed his pyrogeometer from an idea of two-way heat flux E_in and E_out, while understanding that only the net flux E_eff could effectively be measured. But to determine DLR = E_in from (*) E_out had to be known and Ångström then simply assumed that E_out = sigma T^4 as if the Earth surface was radiating like a blackbody into a surrounding of 0 K. Since this is obviously not the case Ångström made an ad hoc assumption about E_out without physical basis, and then reported DLR with a terminology suggesting a physical meaning. But the DLR determined by (*) lacks physical meaning because E_out lacks physical meaning.

Anders Ångström thus opened to an unphysical misconception of two-way radiative heat transfer, while according to Stefan-Boltzmann there is only one-way heat transfer from warm to cold. Anders was not a physicist like his father Knut, and evidently lacked some understanding of the physics of the pyrgeometer.

The unphysical science by Anders Ångström opened to give the atmospheric trace gas CO2 an unphysical warming effect which was later efficiently exploited by climate alarmists.

To understand that a pyrgeometer reporting DLR in W/m2, while effectively recording a temperature difference, is reporting fiction without physical basis, requires going to the bottom of the Stefan-Boltzmann Law and its proof. Since very few people are willing to do so, a constructive debate is lacking.

Both climate alarmists and most of their critics have been misled by Anders Ångström and take for granted that there is something named DLR of some physical meaning which can be connected to CO2 which is evidenced by pyrgeometers. And without critics, climate alarmism continues to oppress humanity, without reason in physics.